Recent years, many medical images showing the interiors of living bodies have been used in medical diagnoses, and, in order to acquire such medical images, various technologies and apparatuses (modalities) such as an X-ray imaging apparatus, X-ray CT (computed tomography) apparatus, ultrasonic (US) diagnostic apparatus, MRI (magnetic resonance imaging) apparatus, and PET (positron emission tomography) apparatus are widely used. Many of the apparatuses are digitalized, and diagnostic information processing systems within hospitals and so on are being constructed. Further, among the imaging technologies, CT and MRI have achieved significant results in detection and evaluation of lesion parts in living bodies because they can acquire and display axial images of a living body at relatively short intervals. Here, an axial image refers to a tomographic image that shows a surface perpendicular or substantially perpendicular to the body axis of an object to be inspected (so-called cross sectional surface). Hereinafter, the axial image is also simply referred to as “slice image”.
At the time of tomographic imaging for CT inspection or the like, not only one part (e.g., only the chest or abdomen) is necessarily imaged, but imaging is often performed over plural parts (e.g., from chest to abdomen, head to chest, or the like) in one inspection. One series of slice images obtained by imaging are typically a thousand and several hundreds to several thousands of images, and therefore, significant effort and burden are taken for display slice images of a part desired by an image interpretation doctor.
As a related technology, the applicant has proposed an image display apparatus capable of reproduction display of sectional images designated by a user (see Japanese Patent Application Publication JP-P2004-167042A). This image display apparatus is an image display apparatus for sequentially displaying plural sectional images continuous in an axis direction while moving the section of the sectional image to be displayed along a direction perpendicular to the section based on three-dimensional image data representing a subject, including designating means for designating a sectional image desired by the user among the sequentially displayed plural sectional images, first storing means for storing a first display parameter for display of the sectional image including a position in the direction perpendicular to the section of the sectional image designated by the designating means, and first image displaying means for displaying the designated sectional image based on the first display parameter stored by the first storing means according to a request of the user (page 2, FIG. 2).
That is, in JP-P2004-167042A, the user designates the desired sectional image, stores the first display parameter for display of the designated sectional image, and displays the designated sectional image based on the stored first display parameter. For the purpose, the user is necessary to designate the sectional image desired by the user. However, one series of slice images are typically a thousand and several hundreds to several thousands of images, and therefore, significant effort and burden are taken for the user to designate the desired slice image.
Further, Japanese Patent Application Publication JP-P2002-253539A discloses a system for enabling efficient management of an enormous amount of medical images by automatically extracting imaging attribute information of imaging apparatus, part, imaging orientation, and so on by image processing from medical images, and adding the information to management information. The medical image identification system is a system for storing and managing medical images, and includes means for classifying an input image, template image storing means for storing template images on categories to be identified with respect to each classification, means for selecting template images of plural categories as candidates of identification using the classification result of the input image, image identifying means for comparing the selected template images with the input image and determining the category of the template image that is the best match, and means for adding manage information the template image has to management information of the input image (page 2, FIG. 1).
That is, in JP-P2002-253539A, the imaged part or the like of the input image is determined by classifying the input image based on the size of the input image, the number of rectangular areas in the input image, and so on, selecting template images of plural categories according to the classification, extracting one that matches the gray scale information and the mosaic image of the input image from the selected template images, and providing the management information (e.g., the imaged part) that has been provided to the template image as management information of the input image.
However, one medical image does not always show only one part. For example, plural parts are often shown in the way that the chest is shown in a portion of an image and the abdomen is shown in another portion of the image. Despite this, JP-P2002-253539A does not disclose anything about part recognition for images that show plural parts.
On the other hand, for a follow-up of a disease or the like, plural times of tomographic imaging on one patient may be performed at great time intervals. In this case, an image interpretation doctor compares slice images obtained at this inspection and slice images obtained at the previous inspection (comparison interpretation), and thereby, can more properly grasp the progress of the disease or the like. Accordingly, conventionally, a medical image display apparatus on which the slice images obtained at this inspection and slice images obtained at the previous inspection are displayed side by side is used.
In such a conventional medical image display apparatus, the image interpretation doctor associates one slice image of the one series of slice images obtained at this inspection with one slice image of one series of slice images obtained at the previous inspection, and allows to display other slice images based on the pair of associated slice images. For example, the image interpretation doctor associates the slice image being displayed within the first area of the display screen (the slice image showing the abdomen part obtained at this inspection) with the slice image being displayed within the second area of the display screen (the slice image showing the abdomen part obtained at the previous inspection).
However, the posture and the size of the lung field of the patient (they change according to the amount of air accumulated within lungs when the patient temporarily stops breathing or the like) may be different between this inspection and the previous inspection. Accordingly, for example, when the image interpretation doctor allows to display a slice image showing the chest part of one series of slice images obtained at this inspection within the first area of the display screen by operating a predetermined key (e.g., cursor move key or the like), the slice image showing a different body part from the body part shown by the slice image displayed within the first may be displayed within the second area of the display screen.
Further, one series of slice images obtained in single imaging are typically a thousand and several hundreds to several thousands of images. Accordingly, significant effort and burden are taken to associate one slice image of the one series of slice images obtained at this inspection with one slice image of one series of slice images obtained at the previous inspection.
As a related technology, Japanese Patent Application Publication JP-A-8-294485 discloses an image display system with which the burden on the image interpreter for comparison interpretation and the time and cost taken for image interpretation can be reduced. This image display system is an image display system for displaying plural sets of three-dimensional images including plural tomographic images acquired by plural times of inspection based on at least one medical image imaging modality on an output device, including designating means for designating at least one pair of first tomographic images in nearly identical anatomical tomographic positions from the plural sets of three-dimensional images, tomographic image pair setting means for setting at least one pair of tomographic images in nearly identical anatomical tomographic positions from the plural sets of three-dimensional images based on a tomographic interval of at least three-dimensional image of the plural sets of three-dimensional images and position information between the pair of first tomographic images, and display controlling means for causing the output device to display the set at least one pair of tomographic images (page 2, FIG. 1). According to the image display system, the very difficult operation of aligning the anatomical tomographic positions can be performed by a simple operation, and the burden on the image interpreter doctor can be reduced.
Further, JP-A-8-294485 also discloses that, in the processing of designating the pair of tomographic images in nearly identical anatomical tomographic positions, the designation processing is automatically performed using feature quantities of the three-dimensional images (paragraphs 136-139 on page 15). Thereby, the need for the image interpreter to designate the pair of tomographic images in nearly identical anatomical tomographic positions can be eliminated.
Furthermore, JP-A-8-294485 also discloses that, when there is no tomographic image in the calculated z coordinate position due to successive display of pairs of tomographic images, the tomographic image nearest the tomographic surface is displayed (paragraphs 148-153 on pages 16-17). Moreover, JP-A-8-294485 also discloses that the subtraction image of the pair of tomographic images is displayed (paragraphs 177-181 on pages 19-20).
In the image display system disclosed in JP-A-8-294485, for automatic designation processing of pair of tomographic images in nearly identical anatomical tomographic positions using feature quantities of the three-dimensional images, three-dimensional correlation calculation or two-dimensional correlation calculation between three-dimensional images is used (paragraphs 136-139 on page 15). However, since the feature quantities of the three-dimensional correlation calculation or two-dimensional correlation calculation between three-dimensional images are very large, there is a problem that processing load is great and the processing time becomes longer. Further, when the posture and the size of the lung field of the patient are different between this inspection and the previous inspection, and when the lesion part becomes larger, the identical anatomical tomographic positions of the pair of tomographic images with the maximum correlation coefficient are not necessarily nearly identical.